Process for treating metals



Feb. 21, 1939.

E. H. GREENBERG PROCESS FOR TREATING METALS Original Filed Dec. 16, 1936 2 Sheets-Sheet 1 INVENTOR f /rneraeenbel BY ATTO NEYS Patented Feb. 21,, i939 PATENT oFricE lPRQClESS lFOR. TREATING METALS 'lElme r 1H. Grecnberg, Philadelphia, Pa.

@riginal application December 16, 1936, Serial No. 116,139. Divided and this application February 20, 1193?, Serial No. 126,821

M claims. (oi. 75-781 This invention relates to a process for treating metals and particularly for det inning lead alloys. It is especially concerned with such process for the production and removal of tin as volatile tin tetrachloride from alloys or mixtures containing lead and tin.

This application is a division of application Serial No. 116,139, filed December 16, 1936.

It is known that chlorine gas will react with lead and tin to form lead chloride and stannous chloride. Stannous chloride in the presence of more chlorine is changed into stannic chloride which is volatile at a known elevated temperature and by heating to that temperature should lzi theoretically be removable from the lead chloride which is not volatile when heated to that tem- Derature. Processes have been heretofore proposed utilizing this principle for separation of tin, but various difficulties have been encountered due 20 in part to lack of appreciation of the proper conditions for operation and in part to the highly corrosive and poisonous nature of chlorine gas, particularlyat high temperatures. The use of chlorine on mixtures of alloys containing lead and 1, tin at low temperatures where the metal is in granular but not melted state, is not practical because the chlorine attacks the exterior of the granules but the chlorides formed then prevent contact of the chlorine with the metals under 30 neath. Operation at higher temperatures has not been practical prior to the present invention, so far as I am aware, because of difficulties in providing a suitable apparatus and process that could be operated economically and eiliciently to produce the desiredresults. 1

The principal object of my invention accordingly is to overcome at least some of the difficulties heretofore recognized and to provide a practical process for the desired removal of tin 40 from mixtures or alloys containing lead and tin with or without other metals. The invention accordingly comprises the novel processes and steps of processes, specific embodiments of which are described hereinafter by way '5 of example and in accordance with which I now prefer to practice the invention.

, The accompanying drawings represent embodiments of apparatus in which the process may be practiced as I now preferto practice it. In these drawings- Fig. 1 is a' diagrammaticelevation partly in section of the apparatus;

Fig, 2 is an enlarged detailsection of the reaction ,chamber; v

Fig. 3 is a cross-section thereof on the line 3-3 of Fig. 2

Fig. 4 is an enlarged detail view of one of the plurality of chlorine pipes passing from a bustle pipe into the reaction chamber; 5

Fig, 5 is a diagrammatic view partly in section of a modification of the kettle and reaction chambers in which two kettles are employed pro vided so that a constant level of molten metal may be maintained easily in the kettle in which the re 0 action chamber is placed;

Fig. 6 is a diagrammatic elevation partly in section of another modification of the apparatus showing three kettles permitting continuous operation of the process; and

Fig. 7 is a diagrammatic elevation partly in section showing a modification of the apparatus shown in Fig. 5 and in place of the second kettle employing a furnace with a bay in which the pump works.

Because of the corrosive and poisonous character of chlorine, especially at temperatures of 1000"-1050 F. at which I prefer to practice the process of the invention as described below, I have shown in the drawings an apparatus in which the chlorine, while combining with the tin, operates in a comparatively restricted area. In that area the apparatus is preferably lined with a chlorineresistant'material which is described and claimed in my copending application Ser. No. 120,877, filed January 16, 1937. In addition the chlorine is confined Within this area so that its escape beyond it in any substantial quantity is prevented. If small quantities pass off with the volatilized tin chloride they are collected by washing, as later described.

Referring now to the drawings and particularly to Figs, 1- to 4, the numeral l designates an open steel kettle supported in a kettle setting 2. 3 is a burner which may be operated by oil or gas and 4 passes through a port in the kettle setting in order to heat the kettle I. l is a framework of channel iron or similar structure extending across the top of the'kettle to support the reaction chamber and other apparatus hereinafter described. 5 is an electric motor mounted on the channel iron 4 and serving to operate the pump 6. This pump per se is described and claimed in my copendingla lp cation Ser. No. 118,704, filed January 2, 1937. The pump is connected by pipe with a cylindrical reaction chamber open at the bottom, which has an outer shell of cast iron 8 lined on the inside g with clay brick 9 ('see'Figs'. 2 and 3). Inside the clay brick 9 isa special concrete layer, In adapted to withstandthecorrosive efiects .of chlorine at about 18 inches.

the temperatures above mentioned. This concrete is that referred to in my copending application Ser. No. 120,877 above, and is composed of crushed fire brick, Portland cement with high alumina content and sand. This cement as shown protects the various parts of the apparatus which it surrounds from the corrosive action of the chlorine gas and molten chloride. The pipe I it will be noted passes through the top of this reaction chamber and terminates a little below the top of the reaction chamber passing through the cement l0 and discharging into a substantially cylindrical space about the center of the reaction chamber, into which space stannic chloride rises on its way out of the reaction chamber. Through the pipe 1 is adapted to be delivered molten lead from the pump 6, the lead being constantly cir- I culated through this chamber. While the pipe is shown as delivering the stream of lead straight downward, it may be inclined at an angle so that the stream of lead will promote a stirring action of the contents in the chamber or the stream may be made to hit a baiile plate to subdivide it.

The reaction chamber a shown is supported by the framework 4 and when in operative position its lower edge will be immersed in the metal inside the kettle to a depth of about 16 inches approximately.

l I is a tank containing chlorine which is led by a pipe I2 to a manifold or bustle pipe 13 which distributes the chlorine to a number of small feed pipes 14. These chlorine pipes arecomposed of special nickel, molybdenum, chromium, iron alloy tubes, preferably the alloy known as Hastelloy C, which is resistant to chlorine and lead and slipped over them, the graphite extending the entire length of the tubes inside the reaction chamber. The graphite tubes are held in place about the steel tubes by a cement Mb consisting of silica sand-finely ground brick and high alumina cement or sodium silicate. .These chlorine pipes extend from the bustle pipe through the cover of the reaction chamber and being of sufficient length so that when the reaction chamber is positioned about 16 inches below the surface of the metal, as indicated above, these chlorine pipes are about 3 to 5 inches below the surface of the metal bath inside the reaction chamber. They surround the central space in the reaction chamber. The bottom edge I 5 of the reaction chamber is about 13 inches below the outlets of the chlorine pipes l4. With these dimensions the diameter of the reaction chamber is approximately 29 inches and its height approximately 31 inches and the length of the chlorine tubes from the cover to their point of discharge in the reaction chamber is The dimensions are given because for the embodiment shown I have obtained excellent results by having the parts proportioned as indicated, although the invention of course is not restricted to such dimensions. These dimen-- sions have been worked out to give a practical reaction chamber. They are such as to provide a proper working depth of lead chloride and stannous chloride but to minimize the quantity of chlorides required for the operation by confining such chlorides in a small space. This is an important consideration because at the end of the operation the amount of chlorides formed in order -to carry out the detinning operation is kept at at minimum and consequently the amount of pure metals recovered is correspondingly larger. '1 I have found that it is important to maintain a sufiicient depth of metal chlorides in the reaction chamber so that with a pressure of 3 to 5 lbs., or perhaps a little more, of chlorine gas as I prefer to use, there .is a suflicient depth of chlorides to react efiiciently with the chlorine and metallic lead and tin entering the chamber so as to avoid use of an excessive quantity of salt layer. The dimensions of the chamber are also such that the amount of surface exposed to the corrosive action of the chlorine and molten chlorides is about as small as could be satisfactorily employed for practical working conditions.

Each of the chlorine feed pipes is connected with the bustle pipe by a T connection in which is provided a cock IS in order to regulate the individual flow through its feed pipe. The upper end of each chlorine pipe is provided with a plug [6a which may be removed in order to clean out the pipe if and when necessary. The numeral ll represents control valves and a flow meter for regulating the amount of chlorine passing to the bustle pipe I3 and thence into the chlorine pipes M. This assembly serves to deliver chlorine gas in a number of fine streams under controlled conditions.

[8 represents a pipe for conducting tin tetrachloride formed in the. reaction chamber away therefrom and into a pre-cooler I9, which is adapted to cool the gases and precipitate any entrained stannous and lead chloride prior to the gases reaching the water-cooled condenser 20 in which the tin tetrachloride is condensed to a liquid which is collected in the container 2! supported therebelow. 22 is a pipe conducting the non-condensable portion of gas passing from 20, and which usually consists of chlorine, to a washing tower 23, which may be filled with a packing material through which dilute caustic soda solution is circulated by the system composed of a sump tank 24 where the caustic soda, after passing through the tower, collects and from which it is pumped by the motor-operated pump 25 and returned to the top of the washing tower by the pipe 26. The apparatus including the pipe 22 and washing tower 23 is not an essential part of the equipment. It is provided to catch any volatile products passing beyond the condenser 20 due to improper operation of the process.

21 is a motor-operated fan connected to the top of the washing tower 23 which serves to keep the entire gas system from-reaction chamber to and including the washer, under a slight vacuum.

'The operation of the apparatus shown in Figs. 1 to 4 is briefly as follows. The metal alloy or other metal mass containing lead and tin, with or without other ingredients, is melted in the kettle I and heated to the temperature employed in operating the process as later described. The pump 6 is started to circulate the molten lead tin through the reaction chamber. Simultaneously chlorine. gas at a measured rate is allowed.

to flow intothe molten metal from the chlorine tank II through the bustle pipe I3 and chlorine feed pipes. Tin tetrachloride is formed in the reaction chamber and volatilized. The vapor leaves the reaction chamber by means of the pipe I8, passes through the pre-cooler l9 where occasionally small amounts of stannous and lead chloride are caught. The cooled tin tetrachloride vapor enters the condenser 20 where it is condensed to a liquid, and is accumulated in the container 2! for subsequent use. If any tin tetraapparatus comprising two kettle settings.

chloride is not condensed or if any chlorine gas should not be consumed in the reaction chamber and pass along with the tin tetrachloride, these materials then pass into the washing system, which is provided as a precautionary measure, passing in at the bottom of the tower 23 where the gases are washed with circulating dilute caustic soda.

In Fig. 5 there is shown a modified form of Kettle 28 is preferably much larger than kettle 29. This apparatus is devised in order that a constant level may be maintained in kettle 39 during the operation. It will be understood of course that in operating, for example as in Fig. l, the mass of molten material in the kettle l gradually becomes lower due to the removal of tin as tetrachloride therefrom. Such lowering of the molten metal may be compensated for by feeding fresh metal into the pot during the early period of treatment, but this should be discontinued if the greater part of the tin is to be separated as tin tetrachloride, if the operation is to be conducted economically. In addition it would be dimcult, if not impossible, to raise and lower he reaction chamber, because of the various feed and delivery pipes connected to it, in order to keep it properly immersed in the shrinking bath if no new metal is added thereto. It is important that the relation of the tips of the chlorine feed pipes with the metal and chloride bath be maintained substantially as indicated above and if there is any substantial deviation the smooth progress of the reaction may be interrupted.

Accordingly I have provided in Fig. 5 an apparatus in which a constant level is maintained in the kettle 29. In this latter kettle the reaction chamber with its outer wall 3, chlorine pipes M,

bustle pipe i3 and other associated parts are thesame as described in Fig. l, and are supported by a casting 30 on the top of the kettle 29. This casting is preferably solid and provides a cover for the kettle 29. The kettle 23. however, contains the pump 6 and pipe l leading therefrom into the reaction chamber. The pump 3 is supported by a casting 3| supported on the edges of the kettle. A pipe 3Ia, serves to circulate the molten .metal between the kettles 38 and 29. When the metal rises above the desired height in kettle 29, it flows over into kettle 2B. Burners 32 and 33 may be introduced through the brick walls of the kettle supports 2 and either or both kettles 23 and 29 may be heated, if desired.

The modification shown in Fig. 7 is similar to that shown in Fig. 5, but kettle 28 in this instance is replaced by a furnace 35, which has an outside bay 35 communicating with the interior, wh ch bay contains a limited quantity of molten metal and in which bay the pump 6 is placed delivering molten metal by pipe I to the reaction chamber. The kettle 29 is supported on a kettle base which in turnis elevated on a steel structure 36. The kettle is supported atsuillcient height so that it is above the furnace 34 and 'so that an overflow pipe 31 will remove molten metal from the kettle 29 and deposit it in the furnace 34 when themetal in kettle 29"rises above the des red level.

The operation of the apparatus shown in Figs. Band 7 is similar to that shown in Fig. 1.

A still further modification is shown-in Fig. 6 to provide apparatus which may be employed for a substantially continuous process. instance three kettles 38 3 9 and ll! areprovided. The center kettle 38 corresponds to the kettle l in Fig. 1 and this kettle operates alternately with In this either kettle 39 or kettle 40. Some time may be lost in heating up a bath of metal to 1000-4050. F. which is the preferred temperature for detinning according to the process of the invention. Considerable time is also lost in cooling the metal bath after detinning so that it may be cast. By the arrangement shown in Fig. 6 practically continuous process may be maintained. While metal in kettle 40 is being detinned, the metal in 39 is being cooled, cast and a new lot introduced, melted and brought up to the temperature above mentioned. The reaction chamber is situated in kettle 38 and with its associated parts is substantially the same as that shown in Fig. 5, being supported by a solid casting which serves as a cover for the kettle 38. Only a single pump 6 may be employed and when it has finished its operation in one kettle, 40 for example, it may be detached and transferred to the other kettle 39 for operation. Overflow pipes 4| and, provided respectively with stoppers 43 and 44, extend from the kettle 39 and deliver into the adjacent kettles, pipe M delivering into kettle 40 and pipe M delivering into kettle 39. The operation of this embodiment is as follows. Metal is charged for instance into kettle 40, heated to a process temperature, pumped through pipe I and delivered into the reaction chamber. Chlorine is delivered from its source through the bustle pipe i3 and chlorine pipes i4 into the reaction chamber and stannic chloride passes oiT through pipe it through the condensing system shown in Fig. 1. During the process the pump 6 is delivering the molten metal as stated through the pipe l to the reaction chamber and the overflow pipe M being ope n by removal of its stopper 43, metal overflows from the kettle 38 into the kettle M and then is again returned by'the pump. Prior to the completion of the detinning of the metal in M, another charge of metal is placed in kettle 39 and heated up to process temperature. When detinning is completed in El] the pump 3 with its piping l is shifted to kettle 39 and the process of detinning similar to that described in connection with kettle 40 is carried on here, but at this time the overflow pipe M is closed by stopper 43 so that the overflow occurs from pipe' d2, its stopper 44 having been removed. While the detinning is occurring in kettle 39, the detinned material in MI is coolingvand being cast. After the detinning in kettle 39, the operation then proceeds in 40 once more. 'In other words the kettles 39 and 40 are alternately used for the heatingand detinning operation and then for the cooling operation.

The process of my invention may be conven iently carried out in the apparatus above described. I have found in accordance with my invention that when chlorine is injected into a molten lead-tin mixture or alloy with or without antimony, lead chloride and stannous chloride are formed and these salts will float to the surface. The reaction involved is:

If further chlorinecomes in contact with these salts-lead chloride and stannous chloride, there will beformed stannic chloride which is volatile at about 238 and the temperature oi the lead chloride and stannous chloride be ng above this point, the stannic chloride will be volatilized and is removed from the mass. chloride is removed, further quantities of stan- As the stannic nous chloride must be formed, which in turn I reacts with a further quantity of chlorine to produce stannic chloride.

I have found in accordance with my invention that it is important to keep the flve chief reacting materials involved in the production of tin tetrachloride from mixtures containing lead and tin, namely tin, lead, stannous chloride, lead chloride and chlorine, all in active contact with one another. It is important to have a large surface of chlorine exposed to the reacting materials. It is also important to keep the metal salts in constant agitation so that the other three reacting materials may come in contact with them. If ordinary mechanical agitators are employed, it is difficult to keep any agitation equipment in operation because of the terrific attack by the chloride at the elevated temperature, which I prefer to be in excess of 1000 F.

I have found that by introducing chlorine into a reaction chamber in contact with molten metal containing tin and lead and perhaps other ingredients, forming a salt layer containing lead and stannous chloride and discharging a stream of molten metal containing lead, tin and perhaps other ingredients through this salt layer, that I can satisfactorily produce tin tetrachloride. Under proper conditions which will be given in greater detail below, the process can be conducted economically and efliciently. Although I do not wish to be bound by the following explanation, there appears to occur under these conditions the establishment of an equilibrium or balance between the components lead chloride, stannous chloride, lead and tin, which balance is being continuously upset by the introduction of further quantities of chlorine. Chlorine reacts with the stannous chloride to form tin tetrachloride which is then volatilized. The equilibrium being upset is then restored by the formation of stannous chloride by reaction of tin with lead chloride. The reactions mentioned are as follows:

Sn+Cl2- SI1C12 SnClz+Clz SnCl4 (tin tetrachloride volatilizes) PbCl2+Sn Pb+SnClz (stannous chloride) Pb+C12- PbCl2 The amnity of the diflerent metals and their lower chlorides or chlorine are such thatvery little antimony or arsenic, if any be present, goes into the saltlayer and the resulting tin tetrachloride contains usually not more than fractions or. percents of either. The heat of they above reactions involving the production of tin tetrachloride and stannous chloride tends to raise the metals-with which it is in contact, nevertheless the temperature of this molten bath because of the large volume of metal therein is lower than that in the reaction chamber and furthermore a certain amount of cooling of this molten metal opcurs during the pumping'operation so that tile molten metal delivered by the pump into the reaction chamber is at a. temperature where it aids in maintaining the temperature of the reaction I chamber within the desired limits. Accordingly after the chlorinating reaction has started in the reaction' chamber, it is ordinarily not necessary to apply heat to the kettle to raise or maintain the temperature of the metal, but if this should be necessary of course the kettle may be heated by the burner shown thereunder in the above embodiments of the apparatus.

The following is a description of an embodiment of the process as I now prefer to practice it:-

A charge of material containing lead and tin usually in the form of a lead alloy of about 80,000 lbs. containing about 12% tin, is heated to 1000-1050 F. for example in the kettle l shown in Fig. 1. Lead chloride has a melting point of approximately 930 F. and I regard it as important to keep the temperature somewhat above this melting point in order to avoid plugging the pipes H through which the chlorine gas emerges. The molten alloy is circulated from the kettle I through the pump 6 and through the reaction chamber and chlorine is fed into the reaction chamber from the tank H. The chlorine reacts with the metal to build up a salt layer of lead chloride and stannous chloride and the molten alloy passing into the reaction chamber is discharged through this salt layer by the pump 6 at a rate of 25,000 to 40,000 lbs. per hour. The reaction chamber as noted in the description of the apparatus is suitably positioned below the surface of the molten metal. Where the diameter of the reaction chamber is about 29 inches and its height approximately 31 inches, the reaction,

chamber will be about 16 inches below the surface of the metal and the ends of the chlorine tubes from the cover of the reaction chamber to their point of discharge will be about 18 inches and they will terminate, therefore, about 13 inches from the bottom of the reaction chamber. The chlorine is delivered to the reaction chamber under a pressure of about 3 to lbs. per square inch and the rate of delivery of the chlorine is controlled by the control valves and meter I1 depending on the amount of tin present in the molten metal. The smaller the amount of tin the less the chlorine conveyed to the reaction chamber. Usually at the beginning of the operation when the metal contains the initial quan tity, 12% of tin, 350 lbs. of chlorine per hour are used and theamount is then tapered down in about the following way:

Percent tin Pounds oi in metal Cl per hour ends'of the chlorine feed pipes become submerged in the salt layer, consisting of lead chloride and stannous chloride. 1 The depth of the chloride layer formed is such that with chlorine gas at 3 to 5 lbs. per sq. inch the chlorine will penetrate to and react as far as the bottom of the layer but will not emerge substantially beyond it. From this time on it appears that the chlorine gas entering the salt layer reacts with the stannous chloride to forma volatile tetrachloride and upon depletion of the stannous chloride in this way the reactions above mentioned to reestablish the equilibrium appear to occur. When the metal left in the kettle I contains above 0.25% tin, the operation is considered finished as this is aboutthe lowest content of tin that can be ordinarily obtained commercially.

The tin tetrachloride produced is preferably conducted to a pre-cooler l9 where any entrained liquids or high boiling liquids, which can be condensed at a higher temperature than that required for tin, tetrachloride, are removed from the tin tetrachloride and returned to the reaction chamber by gravity. The tin tetrachloride vapor then passes to the condenser 20 where it is condensed to a liquid and is accumulated in the container 2i for subsequent use. Any tin tetrachloride not condensed in 20 or any chlorine gas not consumed in the reaction chamber and passed along with the tin tetrachloride is washed out with caustic soda solution. Very little chlorine gas in practice needs to be washed out as the emciency of chlorine absorption in the reaction chamber is high At the end of a run which ordinarily lasts two to three days depending on the original tin content of the metal being treated, there remains in the reaction chamber and floating on the metal bath about 2% of lead chloride of the original weight of alloy treated.

As the tin is eliminated as tin tetrachloride, the level of the metal bath in the kettle I is progressively lowered. As it is important to keep the metallevel approximately constant for efficient operation, I feed in fresh quantities of metal to the kettle l during the run in order to maintain the original level. It is advantageous to use for this purpose metal richer in tin than the original metal so that the production of tin tetrachloride is maintained at the maximum.

I have treated compositions containing not only lead and tin but also containing from 2.5 to 19% antimony and have found that the antimony contents had no adverse, efiects on the removal of the tin. In treating one composition which contained 8% antimony and 5% tin along with the balance lead, the lead chloride produced at the end of the operation contained approximately 0.77% antimony. I have also satisfactorily operated the process on numerous lots of material containing the following ranges of materials:--

1 Per cent Tin 1.7 to 21 Bismuth 0 to 7 Copper Trace to 5 Arsenic 0.1 to 4 Antimony 8 to 26 andthe balance lead. P

i are obtained when lead tin alloys are used which contain substantially no other ingredients or only small proportions of other ingredients which are present as the raw material subjected to the process. I do not add catalysts such as sulfides,

antimony. or other ingredients to the raw mate-:-- .rial being treated, andI prefer'to remove sulphur if it is present in the metal being treated.

In the appended claims where I use the expression leadand tln-containing metal I intend to include lead tin alloys and mixtures of metallic lead and-tin which may or may not contain impurities such as bismuth, copper, arsenic and antimony.

The tetrachloride of tin produced by the process is remarkably pure when considering the impurity of the various compositions treated. I have found it to contain not over .04 to .92% of such impurities with 99.96% to 99.08% of tin tetrachloride. The impurities found in the tin tetrachloride will depend upon the quality of the metal being treated. The apparatus described above has been used satisfactorily in the carrying out of the various process operations described.

A process which comprises among other things the maintenance of a substantially constant level in the kettle where the reaction chamber is located may be carried out for example employing an apparatus like that shown in Fig. 5. The lead and tin are melted in the kettles 28 and 29 and maintained at about 1000-1050 F. as above described, and the pump 6 started in kettle 28,

- chlorine under 3-5 lbs. per sq. inch being fed to the reaction chamber through the tubes M. A chloride layer forms in the reaction chamber floating on the molten metal beneath. Chlorine comes in contact with the chloride layer and the metal being circulated by the pump. The stream of metal passing through the chloride layer passes into the kettle 29 and then overflows through the pipe Ma. into the kettle 28. Stannic chloride is removed through the pipe l8 and may be condensed as heretofore described.

A similar process may be carried out employing the apparatus shown in Fig. '7.

In carrying out a continuous process for separating tin as tetrachloride from alloys of mixtures containing tin and lead, I may employ an apparatus such as that shown in Fig. 6. Here lead and tin are melted in the kettle and maintained at 1000-1050 F. prepared as above described and pumped for example from vessel 40 through the reaction chamber in vessel 38 Where it comes in contact with a plurality of streams of chlorine under 3 to 5 lbs. per sq. inch as above described to form a separate layer of stannous chloride and lead chloride. The stream of molten lead passes through the layer of chlorides after it is formed and stannic chloride is removed from the reaction chamber until the quantity of tin in the molten metal issubstantially reduced. Then a second mass of tin and lead is heated in 'the vessel 39 and circulated through the reaction chamber in contact with the streams of chlorine to form a molten chloride layer and to produce tin chloride. During this operation the metal in 40 is cooling so that it may be cast. It is removed when cool and then prior to the detinning of the material in the kettle 39 a fresh lot of tin and lead is placed in kettle 40 and heated up so that when the detinning operation ceases in kettle 39, another operation may be started on the new metal in kettle 40 so that the process is operated continuously.

While the invention has been described in detail with respect to particular preferred ex amples,.1t will be understood by those skilled in 'the art after understanding the invention, that fore in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent of the United States is:-

1. A process for separating tin from alloys or mixtures containing tin and lead which-comprises, melting leadand tin-containing metal, bringing chlorine gas into contact with said metal in the presence of a separate layer of stannous chloride and lead chloride, moving said molten metal from below said layer and discharging it into said layer so that it reacts therewith in the presence of said chlorine, thereby forming stannicchloride.

2. A process for separating tin from alloys or 'mixtures containing tin and lead which comprises melting leadand tin-containing metal, bringing a plurality of streams of chlorine gas into contact with the molten metal to form a stannous chloride and lead chloride layer, and conducting the streams after formation of said layer into contact with a mixture ofv the molten metal and said chlorides in proximity to the junction of said layer with the molten metal below.

3. A process for separating tin from alloys or mixtures containing tin and lead, which comprises melting leadand tin-containing metal, bringing a pluralityoi. streams of chlorine gas into contact with said metal in a reaction chamber to form a layer of stannous chloride and lead chloride, moving said molten metal from below said layer and discharging it into said layer so that it reacts therewith in the presence of chlorine, thereby forming stannic chloride.

4. A process for separating tin from alloys or mixtures containing tin and lead, which comprises melting leadand tin-containing metal, bringing a plurality of streams of chlorine gas into contact with said metal in a reaction cham her to form a layer of stannous chloride and lead chloride, moving said molten metal from below said layer and discharging it into said layer so that it reacts therewith in the presence of chicrine, thereby forming stannic chloride, and removing and condensing the stannic chloride formed.

5. A process for separating tin from alloys or mixtures containing tin and lead, which comprises melting leadand tin-containing metal, bringing a plurality of streams of chlorine gas into contact with said material in a reaction chamber to form a layer of stannous chloride and lead chloride, maintaining a salt layer of stannous chloride and lead chloride at a temperature of approximately 1000-1050 F., moving said molten metal frombelow said layer and discharging it into said layer so that it reacts therewith in the presence of chlorine, thereby forming stannic chloride.

6. A process for separating tin from alloys or mixtures containing tin and lead, which comprises melting lead and tin containing metal, bringing chlorine gas in the form of fine streams into contact with said metal, in the presence of a separating layer of stannous chloride and lead chloride and maintaining said layer at a temperature below the boiling point of stannous chloride and above the melting point of lead chloride and stannous chloride, pumping said molten metal from below said layer anddischarging it into said layer so that it reacts therewith in the presence of chlorine, the quantity of molten metal so pumped and'discharg'ed being equal to several times the volume of the metal'being operated upon, thereby forming and volatilizing stannic chloride.

7. A process for separating tin from alloys or mixtures containing tin and lead, which comprises melting leadand tin-containing metal, bringing a plurality of streams of chlorine gas at low pressure into contact with the molten material to form a stannous chloride and lead chloride layer, the streams of chlorine being conducted into contact with and through the molten chlorides at about the junction of said layer with the molten metal below, moving said molten metal from below said layer and discharging it into said layer so that it reacts therewith in the presence of chlorine, thereby forming stannic chloride, and reducing the amount of chlorine gas fed to the molten metal as the amount of tin decreases in the molten mass.

8. A step in the process of separating tin from alloys or mixtures containing tin and lead, which consists in moving a molten mass of lead and tin containing metal through a salt layer of lead chloride and stannous chloride lying on top of a molten bath containing lead and tin in the presence of a plurality of streams of chlorine.

9. A continuous process for spearating tin from alloys or mixtures containing tin and lead, which comprises melting the leadand tin-containing metal in a vessel, pumping the molten metal through a reaction chamber into a second vessel and as it passes through the reaction chamber bringing it in contact with a plurality of streams of chlorine gas to form a separate layer of stannous chloride and lead chloride, the stream of molten lead and tin metal passing through said layer, forming and removing stannic chloride from the reaction chamber until the quantity of tin in the molten metal is substantially reduced, melting a second mass of tin and lead containing metal in a third vessel prior to the complete detinning of the material in the first vessel and when the metal in the first vessel has been sufficiently detinned, continuing the operation in the third vessel by pumping metal therefrom through the reaction chamber and into the second vessel while subjecting it to a plurality of streams of chlorine gas, thereby forming and liberating stannic chloride, meanwhile allowing the metal in the first vessel to cool, and removing it from the first vessel and prior to the detinning of the metal in the third vessel, heating up a fresh charge in the first vessel and conducting the operation continuously alternately in the first and third vessels in cooperation with the reaction chamber in the second vessel to continuously produce stannic chloride.

10. A process for separating tin from alloys orv mixtures containing tin and lead, which comprises melting a mixture of the lead and tin in a vessel, pumping the molten metalthrough a reaction chamber into a second vessel and as it passes through the reaction chamber bringing it into contact with a plurality of streams of chlorine gas to form a separate layer of stannous chloride and lead chloride, the stream of molten lead and tin passing through said layer and forming and removing stannic chloride from the reaction chamber until the quantity of tin in the molten metal is substantially reduced whereby the level of the metal surrounding the reaction chamber may be maintained substantially constant regardless of the amount of tin removed as tin chloride.

-11. A process for separating tin from alloys or mixtures containing tin and lead, which comprises forming a layer containing molten tin and l i A lead chlorides in a reaction chamber, passing molten lead and tin through said layer and simultaneously supplying chlorine under a pressure of about 3 to 5 pounds per square inch in a plurality of jets into contact with the chlorides and molten lead and tin, and allowing the layer or chlorides to build up in the reaction chamber so that the chlorine under the pressure indicated is about sumcient to move to and react as far as the bottom of the mass of chlorides, but not beyond the bottom of the chloride mass sufliciently to form any substantial amount oi'chlorides in the metal bath.

12. A step in the process of separating tin from alloys or mixtures containing tin and lead which consists in bringing chlorine gas and molten leadand tin-containing material into a bath having similar molten leadand tin-containing material in the lower portion and alayer of molten chlorides rides, and causing a heat-producing reaction to occur in proximity to the chloride layer thereby raising the temperature of said layer, and'delivering further portions of somewhat cooled alloy to the materials being chlorinated.

ELMER H. GREENBERG. 

